The invention relates to magnetic tape having markers at the beginning and end of the tape for indicating to a recording device that a tape boundary is approaching. More particularly, it relates to optically detectable beginning-of-tape (BOT) and end-of-tape (EOT) indicators on the magnetic tape.
Today""s tape drives can wind tape at remarkably high speeds. Although these high speeds decrease the amount of time required to store and read archived data, the tape is subjected to considerable physical stress during acceleration and deceleration of the reel. Furthermore, the tape may be torn from the reel if the end of the tape is reached at high speed. Devices that record data onto magnetic tape benefit from markers indicating that the beginning or end of the tape is approaching so that the acceleration or deceleration may be controlled to minimize the force applied to the tape. Such markings are referred to as beginning-of-tape (BOT) and end-of-tape (EOT) indicators. A common method for creating BOT and EOT indicators is to create a physical hole in the magnetic tape at an appropriate location. These holes are detected by an optical transmitter/receiver as the area of the tape containing the hole passes the transmitter/receiver.
Creating physical holes in the magnetic tape is, however, highly disadvantageous, because the presence of such holes creates a physical distortion in the magnetic tape associated with various readback problems. As the tape winds onto a takeup or supply reel, the next several wraps are unsupported over the area of the hole. The tape acquires a physical deformation, called embossing marks, which roughly approximate the geometry of the hole. Multiple embossing marks are created in the tape, with a spacing approximately equal to the circumference of the reel. These marks diminish with increasing distance from the hole.
Embossing marks are associated with data readback errors. They create distortions in the readback signal which can lead to amplitude-or timing-related errors. Also, the physical deformation of the tape can cause the tape to move away from the reading head. In addition, loose debris can accumulate around the edges of the BOT and EOT holes, which can transfer to the tape recording head and can cause readback errors.
Accordingly, an object of the present invention is to provide BOT and EOT indicators which do not result in embossing marks on the magnetic tape.
Another object of the present invention is to provide BOT and EOT indicators which are detectible by an optical transmitter/receiver.
The objects above are accomplished by the alteration of one or more discrete areas of the recording layer or the non-recording layer of the magnetic tape. The removal of one or more discrete areas of either the recording layer or the non-recording layer of the magnetic tape results in a marking detectible by an optical transmitter/receiver. Alternatively, the placement of a fluorescent or optical dye on the recording layer or the non-recording layer of the magnetic tape results in a marking detectible by an optical transmitter/receiver.
The systems and methods described herein further provide methods for creating BOT and EOT indicators by removing a discrete area or areas of the recording layer or the non-recording layer of a magnetic tape, such that an optical signal is detectible through the remaining layers of the magnetic tape.
The systems and methods described herein also provide a method for creating BOT and EOT indicators by placement of a fluorescent or optical dye on the recording layer of a magnetic tape. Such a fluorescent or optical dye is optically detectible, and further eliminates any physical distortion in the magnetic tape.